颚裂（英语：cleft chin）亦称颏裂、裂下巴或酒窝颚（dimple chin）、屁股下巴，是一种常见而具遗传性的面部特征，指人们头部的下颌位置皮肤有酒窝或类近的深窝。具有该特征的人因为底层骨骼的特殊性而在下颌呈现出条状或近乎倒Y字体的凹陷。

这种凹陷是源于下颚骨骼或其上的颏肌（Mentalis muscle）的左右两半部分连接不完整，导致下颌骨出现沟隙所引起；主要属于先天性的遗传现象，因此颚裂在胚胎及胎儿发展期间便会逐步形成。其余较少数具有颚裂特征的人则往往是随着时间的推移，令下颌某一旁的肌肉逐渐下垂或长于另一旁的肌肉而导致面容不对称。

The terms cleft chin, chin cleft, dimple chin, or chin dimple, refer to a dimple on the chin. It is a Y-shaped fissure on the chin with an underlying bony peculiarity. Specifically, the chin fissure follows the fissure in the lower jaw bone that resulted from the incomplete fusion of the left and right halves of the jaw bone, or muscle, during the embryonal and fetal development. For other individuals, it can develop over time, often because one half of the jaw is longer than the other, leading to facial asymmetry.